Collet Fixation System

ABSTRACT

A bone fixation assembly which may include a bone fixation element, a collet and a flexible line. The bone fixation element may comprise a first and second passageway and at least the first passageway is configured to receive the collet. The flexible line passes through both passageways and is secured through the second passageway. The collet may be advanced into the first passageway causing the collet to circumferentially engage the flexible line fixing it in place. Instrumentation for securing the collet includes a collet driver, a counter torque instrument and a tensioner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of:

Pending U.S. patent application Ser. No. 12/341,326, filed Dec. 22,2008, which carries Applicants' docket no. MLI-73, and is entitledCOLLET FIXATION SYSTEM.

U.S. patent application Ser. No. 12/341,326 claims the benefit of:

Expired U.S. Provisional Patent Application No. 61/015,374, filed Dec.20, 2007, which carries Applicants' docket no. MLI-73 PROV, and isentitled COLLET FIXATION SYSTEM.

The above mentioned documents are incorporated by reference herein intheir entirety.

The following disclosure is incorporated by reference herein in itsentirety:

U.S. Pat. No. 7,172,595, filed Jun. 2, 2005, which carries Applicants'docket no. 13447.46.1, and is entitled BONE FIXATION SYSTEMS AND RELATEDMETHODS.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates generally to the attachment of a bonefixation assembly to a bone, and more particularly, to cerclage wiringand to systems and methods for implanting fixation systems to securebone fragments together or to secure prostheses to bone.

2. The Relevant Technology

Cerclage wiring is a technique in which surgeons tie pieces of bonetogether using metal wire or cable. This is commonly done in traumacases to repair fractures and can include a variety of bones and partsof bones including patella, olecranon, femur, trochanter, tibia, etc. Insome cases cerclage wiring has also been using in hip replacements—ifthe patient has poor bone stock in the femur, the surgeon may insert theimplant into the femur and then tie cables and plates to the bone aswell to help support the implant and keep it from breaking out of thebone. This is common known as periprosthetic cerclage.

One difficult aspect of cerclage wiring is providing retensioning of thewire or cable. In some cases the cable is passed through a cablereceiving element and the cable and/or the cable receiving element iscrimped or deformed in some manner to prevent withdrawal of the cablethrough the element. Although this method can be effective it may createa loosening of the cable when crimping. In addition the cable and thecable receiving element are irreversibly deformed disallowingretightening or adjustment.

Other techniques include a button or a pin attachment of the cable to acable receiving element. Again, these may cause permanent deformity ofthe cable disallowing retightening or adjustment.

Other systems may also have set screws that are not in line with thecable and when the screws are tightened against the system the screwspress against the cable. This system along with many other designscauses damage or deformation of the cable.

With either of these techniques a larger incision may be requiredbecause of the need for multiple instruments to tension the cable andcrimp the cable, the element or both. Furthermore the inability toretighten the cables may result in a greater number of cables being usedand a greater amount of time for surgery.

As the above described techniques illustrate, the existing systems andprocedures for cerclage wiring may not be as effective as desired.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present invention will now be discussed withreference to the appended drawings. It is appreciated that thesedrawings depict only typical embodiments of the invention and aretherefore not to be considered limiting of its scope.

FIG. 1 illustrates a cross-sectional side view of a bone, a bonefixation assembly with a flexible line, a collet, a bone fixationelement and a bone fixation instrument assembly with a collet driver anda counter torque instrument.

FIG. 2 illustrates a front perspective view of the bone fixation elementof FIG. 1;

FIG. 3 illustrates a back perspective view of the bone fixation elementof FIG. 1;

FIG. 4 illustrates a side view of the bone fixation element of FIG. 1;with a bone engagement surface, a top portion, a first end and a secondend;

FIG. 5 illustrates a top view of the bone fixation element of FIG. 1;

FIG. 6 illustrates a top cross-sectional view of the bone fixationelement of FIG. 1;

FIG. 7 illustrates a perspective view of the collet of FIG. 1;

FIG. 8 illustrates a top view of the collet of FIG. 1;

FIG. 9 illustrates side cross-sectional side view of the collet of FIG.1;

FIG. 10 illustrates a perspective view of the bone fixation element andcollet of FIG. 1, the collet entirely within a first passageway;

FIG. 11 illustrates a perspective view of the bone fixation element andcollet of FIG. 1, the collet partially within the first passageway;

FIG. 12 illustrates a perspective view of a separate embodiment of abone fixation element with a first end, a first passageway and a secondpassageway;

FIG. 13 illustrates a perspective view of the bone fixation device ofFIG. 12;

FIG. 14 illustrates a side view of the bone fixation device of FIG. 12;

FIG. 15 illustrates a front view of the bone fixation device of FIG. 12;

FIG. 16 illustrates a top cross-sectional view of the bone fixationdevice of FIG. 12;

FIG. 17 illustrates a perspective view of a bone plate fixation elementwith multiple passageways;

FIG. 18 illustrates a perspective view of the bone fixation element andthe bone fixation instrument assembly of FIG. 1, and a bone;

FIG. 19 illustrates an exploded perspective view of the bone fixationinstrument assembly and bone fixation assembly of FIG. 1;

FIG. 20 illustrates a blown up perspective view of a distal portion ofthe counter torque shaft of FIG. 1;

FIG. 21 illustrates a slightly back exploded perspective view of thebone fixation instrument assembly of FIG. 1;

FIG. 22 illustrates a perspective view of a bone fixation instrumentassembly of FIG. 1; and

FIG. 23 illustrates a perspective view of a bone fixation instrumentassembly, collet and bone fixation element of FIG. 1, the collet engagedwith the collet driver.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to systems and methods for bone fixationelements and instrumentation for securing prosthetics to bone, fragmentsof bone together, bone to bone, tissue to bone or tissue to tissue.Those of skill in the art will recognize that the following descriptionis merely illustrative of the principles of the invention, which may beapplied in various ways to provide many different alternativeembodiments. This description is made for the purpose of illustratingthe general principles of this invention and is not meant to limit theinventive concepts in the appended claims.

One embodiment of the present invention includes a bone fixation elementwith at least two passageways, a collet, a flexible line that passesthrough the collet and passageways, and bone fixation instrumentation.The instrumentation also comprises bores or passageways that allow theflexible line to pass through. The flexible line is preferably a polymercord but may comprise a polymer cable, a metal cord or a metal wire,among others. A method of securing the bone fixation element includessecuring one end of the flexible line to or within a first passageway,which may include a collet, of the bone fixation element and passing theline around the bone fragments and passing the flexible line through thebone fixation element through a second or separate passageway, whichincludes a collet. The flexible line passes through the collet andthrough the instrumentation. The flexible line may be tensioned with atensioner as the collet advances into the bone fixation element causingthe collet to circumferentially engage the flexible line securing theflexible line within the collet, which collet is within the bonefixation element. With circumferential engagement of the flexible lineminimal deformation or damage occurs to the flexible line.

Referring to FIG. 1, a bone fixation instrument assembly 600 comprises acollet driver 400 and a counter torque instrument 500. The countertorque instrument 500 and the collet driver 400 are engaged with a bonefixation assembly comprising a bone fixation element 100 and a collet200. A flexible line 800 comprises a first working portion 802 and asecond working portion 804 connected to the first working portion 802.The flexible line 800 engages the bone fixation element 100 with thesecond working portion 804. The second working portion 800 is secured tothe bone fixation element 100. The flexible line 800 wraps around bonefragments or a bone 700 and slidably passes through the collet 200, thebone fixation element 100, the collet driver 400, and the counter torqueinstrument 500. The first working portion 802 is secured to the bonefixation element 100 by advancing the collet 200 into the bone fixationelement 100. The collet 200 circumferentially compresses around thefirst working portion 802, thus fixing it to the bone fixation element100.

FIGS. 2-6 illustrate an embodiment of a bone fixation element with atleast two passageways provided for a flexible line to pass through. Thebone fixation elements described herein may comprise any biocompatiblematerial including stainless steel, titanium, cobalt chrome, othermetals or metal alloys, or polymers, including polyetheretherketone(PEEK), or any bioabsorbable materials.

Referring to FIGS. 1 and 2, a bone fixation element 100 includes a firstend 102, a second end 104 opposite the first end and a top portion 112connecting the two ends 102, 104. A first passageway 106 traverses thebone fixation element from the first end 102 to the second end 104 andmay include threads 114. The threads 114 may be used to secure thecollet 200 within the first passageway 116. A second passageway 108,which may be separate from the first passageway 106, traverses the bonefixation element 100 from the second end 104 to the first end 102. Thesecond passageway 108 may be radially smaller and longitudinally shorterthan the first passageway 106. The passageways 106, 108 may be partiallyor fully enclosed. The first end 102 may include slots 110 which may beequally spaced around an opening for the first passageway 106. Each slot110 is generally circular in shape; however each slot 110 may be anygeometric shape providing an interface for the counter torque instrument500 with a complimentary fit. The counter torque instrument 500 may beinserted into the slots 110 providing counter torque when collet 200 isadvanced into the first passageway 106.

Referring to FIG. 3, the bone fixation element 100 is illustrated fromthe opposite viewpoint of FIG. 2. The second passageway 108 may slidablyreceive a flexible line 800.

Referring to FIG. 4, the bone fixation element 100 includes a boneengagement surface 116 which may be concave. The concavity of the boneengagement surface 116 may compliment that of a bone (not shown) or bonefragments (not shown) on which the bone fixation element 100 is placed.The bone engagement surface 116 may include protrusions (not shown)extending from the surface including, but not limited to, ridges, prongsor teeth which may aid in securing the bone fixation element to thebone.

Referring to FIGS. 1, 5 and 6, the distance between the first end 102and the second end 104 of bone fixation element 100 may vary. The lengthof the first passageway 106 may be greater or less than the length ofthe second passageway 108. The first passageway 106 may taper whenmoving from the first end 102 to the second end 104 forcing the collet200 to circumferentially compress and secure the first working portion802 of the flexible line 800 within the collet. The threads 114extending within the first passageway 106 from the first end 102 to thesecond end 104 may equal to or greater than the length of thecomplimentary collet threads, thus allowing the collet 200 to becompletely inserted into the bone fixation element 100 without any partof the collet protruding. The second passageway 108 is configured toreceive the second working portion 804 of the flexible line 800 as welland may be secured with a knot (not shown) tied in second workingportion 804, preventing withdrawal of the flexible line 800 through thesecond passageway 108. It will be appreciated that any means known inthe art may be used to prevent withdrawal of the flexible line 800through the second passageway 108, including but not limited to crimps,pins, screws or buttons which may engage the line outside of and/orwithin the second passageway to prevent the withdrawal.

Other possible means for securing the collet 200 to the bone fixationelement 100 may include a snap feature (not shown) with a first snapinterface on the collet 200 and a second snap interface on the bonefixation element 100. The bone fixation element 100 may include multiplesnap interfaces preventing withdrawal of the collet 200 thus allowingthe collet 200 to slide further within the first passageway 106 byengaging each successive snap interface deeper within the firstpassageway 106 compressing the collet 200 further with each successivesnap.

FIGS. 7-9 illustrate an embodiment of a collet with a central bore andat least one slit. Referring to FIGS. 7 and 8, the collet 200 includes afirst portion 202, a second portion 204 and a central bore 208 whichextends longitudinally through the collet. The central bore 208 allowsthe passage of the flexible line 800 through the collet.

The first portion, or engagement portion, 202 may engage with the bonefixation element 100. The engagement portion 202 may comprise threads210 or may comprise a snap feature (not shown) to enhance engagementwith the bone fixation element. The threads 210 provide threadableengagement with the first passageway 106. A snap feature (not shown) onthe collet 200 may be configured with a snap interface configured tointeract with a snap feature of the bone fixation element 100. The firstengagement portion 202 also includes a collet driver interface 214providing a means for attachment of the collet driver 400. The colletdriver interface 214 may be a hexagonal shape bore, which may be part ofthe central bore 208, allowing the collet driver 400 with acomplimentary interface to be inserted into the central bore 208. Thecollet driver interface 214 need not be hexagonal in shape, but may besquare, triangular or any shape which may engage with any instrument orother means known in the art for driving or advancing a collet or otherlike fastener.

Referring to FIG. 9, the second portion 204 may comprise at least oneslit 206 allowing the second portion 204 to circumferentially compresswhen advanced into the first passageway 106. The second portion 204 mayfurther comprise ridges 212 formed within the central bore 208. Theridges 212 may be any protrusion including threads, prongs or teeth. Theridges 212 may enhance the engagement between the collet 200 and thefirst working portion 802 of the flexible line 800.

The collet 200 may be tubular, cylindrical or conical or the like andalso may taper or narrow toward one end of the collet, such that thediameter of one end of the collet is greater than a diameter at theopposite end. The collet may be comprised of any biocompatible materialincluding stainless steel titanium, cobalt chrome, polymer, includingpolyetheretherketone (PEEK), or any bioabsorbable materials.

Referring to FIG. 10, the collet 200 is shown in a first engagedposition in which it is positioned entirely within the bone fixationelement 100 to provide a flush surface with the first end 102. Thecollet 200 may also be further within the bone fixation element 100 suchthat the collet is advanced beyond being flush with the first end 102.The first engaged position of the collet 200 circumferentially engagesthe first working portion 802 of the flexible line 800 holding it in afixed position.

Referring to FIG. 11, the collet 200 is in a second position positionedat least partially within the bone fixation element 100. The secondposition allows the first working portion 802 of the flexible line 800to slidably pass through the collet 200. However, another embodiment mayprovide for the collet to engage and lock the position of the flexibleline while positioned only partially in the bone fixation element.

The threadable collet 200 in conjunction with the threadable bonefixation element 100 also allows for loosening of the collet 200 whichallows for additional tensioning of the flexible line 800. The collet200 can be loosened and retightened within the bone fixation element 100disengaging and engaging and fixing the flexible line 800.

Furthermore the system of the flexible line 800, the bone fixationelement 100 and the collet 200, with its circumferential engagement,maintains everything in line such that the first working portion of theflexible line, the collet and first passageway are co-axial. This linemay also be true with the instrumentation including the counter torqueinstrument 500 and the collet driver 400.

FIGS. 12-16 illustrate an alternate embodiment of a bone fixationelement with at least two passageways, wherein two separate collets maybe inserted, providing for a flexible line to pass through. Referring toFIG. 12, an alternate embodiment of a bone fixation element 300 includesfirst end 302, a top portion 312 and a second end 304. A firstpassageway 306 traverses the bone fixation element 300 from the firstend 302 to the second end 304. A second passageway 308, which may beseparate from the first passageway 306, traverses the bone fixationelement 300 from the second end 304 to the first end 302. The first end302 may include slots 310 which may be equally spaced around an openingfor the first passageway 306. Each slot 310 as shown is generallycircular in shape; however each slot 310 may be any geometric shapeproviding an interface for the counter torque instrument 500 with acomplimentary fit. The counter torque instrument 500 may be insertedinto the slots 310 providing counter torque when the collet 200 isinserted into a first passageway 306. The second end 304 may alsoinclude slots 310 with the same structure and function as thosepreviously described. The first and second passageways 306, 308 may alsoinclude threads which extend at least partially through the first andsecond passageways 306, 308 from the first end 302 and second end 304respectively.

Referring to FIGS. 13 and 14, the bone fixation element 300 includes abone engagement surface 316 which may be concave. The concavity of thebone engagement surface 316 may compliment that of a bone (not shown) orbone fragments (not shown) on which the bone fixation element 300 isplaced. The bone engagement surface 316 of this embodiment may alsoinclude protrusions (not shown) extending from the surface including,but not limited to, ridges, prongs or teeth which may aid in securingthe bone fixation element to the bone.

Referring to FIGS. 15 and 16, the first passageway 306 may taper fromthe first end 302 to the second end 304. The taper forces the collet 200to circumferentially compress as it is advanced into the passageway,securing the first working portion 802 of the flexible line 800 withinthe collet 200. Threads 314 may extend within the first passageway 306from the first end 302 to the second end 304 to a length equal to orgreater than the length of the complimentary collet threads 210, thusallowing the collet 200 to be inserted entirely into the firstpassageway 306 without any part of the collet 200 protruding (such as inFIG. 10). The second passageway 308 may taper from the second end 304 tothe first end 302 forcing a second collet 200 to circumferentiallycompress and secure the second working portion 804 of the flexible line800 within the second collet 200. Threads 314 may extend within thesecond passageway 308 from the second end 304 to the first end 302 to alength equal to or greater than the length of the complimentary colletthreads 210 similar to the first passageway 306, allowing the collet 200to be inserted entirely into the second passageway 308 without any partof the collet 200 protruding (such as in FIG. 10).

Other possible means for securing each of the collets 200 to the bonefixation element 300 may include a snap feature (not shown) with a firstsnap interface on the collet and a second snap interface on the bonefixation element 300. The bone fixation element 300 may include multiplesnap interfaces preventing withdrawal of the collet 200 thus allowingthe collet 200 to slide further within the first and second passageways306, 308 by engaging each successive snap interface deeper within thepassageways 306, 308, collapsing the collet 200 further with eachsuccessive snap.

Referring to FIG. 17, an alternate embodiment of the bone fixationelement is a bone plate fixation element 900, similar to a bone plate,which may include two or more passageways. This alternate embodiment maycomprise multiple passageways, at least one of such passagewaysconfigured to engage at least one collet 200. The method for flexibleline 800 engagement is be the same or similar to the bone fixationelement 100 and 300 embodiments, but using multiple flexible lines, or asingle flexible line extending through multiple passageways, secured byat least one collet. The bone plate fixation element 900 may alsoinclude components similar to those found on the previously disclosedembodiments such counter torque slots and a concave bone interfacesurface which may include protrusions.

Any of the possible embodiments of the bone fixation element maycomprise any biocompatible material including stainless steel, titanium,cobalt chrome, polymer, including polyetheretherketone (PEEK), or anybioabsorbable materials.

FIGS. 18-23 illustrate a bone fixation assembly system with a countertorque instrument, a collet driver, a collet, a bone fixation elementand a cable. Referring to FIG. 18, a bone fixation instrument assembly600 includes a collet driver 400 and a counter torque instrument 500.Bone fixation instrument assembly 600 is suitable for use with the bonefixation elements disclosed herein, or with a similar device.

Referring to FIG. 19, the collet driver 400 includes a proximal handleportion 402, a distal portion 406, and a collet driver shaft 404extending between the proximal handle portion 402 and the distal portion406. The proximal handle portion 402 may be radially larger than thecollet driver shaft 404 and the collet driver shaft 404 may be radiallylarger than the distal portion 406. The proximal handle portion 402 mayhave ridges or grips which allow for easier manipulation of the colletdriver 400. The distal portion 406 includes a collet engagementinterface 408 which is slidably insertable into the collet 200 to engagethe collet driver interface 214. Like the collet driver interface 214the collet engagement surface 408 may be any shape that compliments thecollet driver interface 214.

The collet driver 400 also includes a collet driver bore 410 whichextends longitudinally through the collet driver 400. The collet driverbore 410 is large enough to slidably receive the flexible line 800 (notshown) which has been routed around the bone 700 or bone fragments (notshown) through the bone fixation element 100 and the collet 200.

The counter torque instrument 500 includes a counter torque handle 502and a counter torque shaft 504. The counter torque shaft 504 ispositioned distal the counter handle 502 and a first arm 512 of thecounter torque handle 502 extends non-parallel to the counter torqueshaft 504. The counter torque shaft 504 includes a shaft proximalportion 508 whereat the first arm 512 may engage the counter torqueshaft 504. The counter torque shaft may also comprise a shaft distalportion 510. At the distal end of the shaft distal portion 510 there isa key 511 which may be comprised of prongs 514 extending parallel to thecounter torque shaft 504. The prongs 514 are configured to slidablyengage the slots 110 of the bone fixation element 100, and thus may becircular as shown or any other shape complementing the slots 110. Theengagement of the key 511 provides counter torque to the collet driver400 as the driver is rotated to advance or remove a collet.

FIG. 20 provides a larger view of the of the counter torque shaft 504showing more detail regarding the shaft distal portion 510 comprisingthe key 511 comprising prongs 514. The prongs 514 may also engage thebone fixation element 100 by alternate means including forcibleengagement or snap fit engagement.

Referring to FIGS. 19 and 21, the counter torque shaft 504 furthercomprises an outer wall defining a shaft bore 506 that is large enoughto slidably retain the collet driver shaft 404. The collet driver 400 isable to be manipulated within the shaft bore 506 allowing the colletdriver 400 to rotate independent from but coaxial with the shaft bore506. The counter torque handle 502 may further comprise a second arm 518extending non-parallel to the first arm 512. The second arm 518 maycomprise an elbow 524 and a handle distal portion 522. The handle distalportion 522 of the second arm 518 comprises a second arm bore 520. Thesecond arm bore 520 is coaxial with the shaft bore 506. The second armbore 520 may be radially smaller at its distal end than at its proximalend. The counter torque handle 502 may further comprise a notch 516between the shaft bore 506 and the second arm bore 520. With the firstarm 512 and second arm 518, the counter torque handle 502 may resemble a“C” or a “U” shape. The counter torque handle 502 is positioned suchthat the proximal handle portion 402 of the collet driver 400 may residein the notch 516.

The second arm bore 520 is configured to slidably receive a tensioner(not shown) at least partially within the proximal end of the second armbore 520. The tensioner is configured to receive the flexible line 800and provide tension control to the flexible line 800. Actuation of thetensioner engages the flexible line 800 to provide tension to theflexible line 800. The tensioner may be any type of instrument known inthe art configured to tension a flexible line or cable.

Other means of tensioner engagement to the counter torque handle 502 mayinclude forcible insertion into the second arm bore 520, or the secondarm bore 520 may comprise threads wherein the tensioner may bethreadably inserted into the second arm bore 520.

Referring to FIG. 22, the second arm bore 520 is further coaxiallyaligned with the collet driver bore 410 wherein the collet driver 400 ispositioned within the counter torque shaft 504. The alignment of eachbore provides slidably passage of the flexible line 800 (see FIG. 1).

Referring to FIG. 23, the collet 200 is attached to the collet driver400 at the collet engagement surface 408 (not shown in this figure). Thecollet 200 is in an open position allowing for slidable insertion of thecable through the collet 200 through the collet driver 400 and throughthe second arm bore 520.

It will be appreciated that the bone fixation system is capable ofperforming to secure a collet without the counter torque instrument 500.Counter torque may be provided by any means known in the art. Withoutthe counter torque instrument 500 a tensioner would be coupled to thecollet driver 400 to provide tension to the flexible line 800.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. For example,above are described various alternative examples of bone fixationelements for providing cerclage attachment of bone fragments or bone toprosthesis. It is appreciated that various features of theabove-described examples can be mixed and matched to form a variety ofother combinations and alternatives. It is also appreciated that thissystem should not be limited to bone fragments or bone to prosthesis.This bone fixation system may also be used to attach any soft tissue tobone or soft tissue to soft tissue. As such, the described embodimentsare to be considered in all respects only as illustrative and notrestrictive. The scope of the invention is, therefore, indicated by theappended claims rather than by the foregoing description. All changeswhich come within the meaning and range of equivalency of the claims areto be embraced within their scope.

1. A system comprising: a bone fixation element comprising a first end,a second end opposite the first end, and a first passageway extendingbetween the first and second ends; a first collet comprising a firstportion, a second portion, and a central bore extending longitudinallybetween the first and second portions, wherein the first collet ismovable along the first passageway between a first engaged position anda second position; and a line comprising a first working portion and asecond working portion connected to the first working portion, whereinthe first working portion passes through the central bore of the firstcollet, wherein the second working portion is secured to the bonefixation element; wherein, in the first engaged position, the firstworking portion of the line is held in a fixed position relative to thebone fixation element by the first collet, and the first collet is afirst distance from the second end of the bone fixation element;wherein, in the second position, the line slidably passes through thefirst collet, and the first collet is a second distance from the secondend of the bone fixation element, wherein the second distance is greaterthan the first distance.
 2. The system of claim 1, wherein the firstpassageway comprises first threads and the first portion comprisessecond threads which are complementary to the first threads, wherein thefirst collet is secured within the first passageway by the complementaryfirst and second threads.
 3. The system of claim 1, wherein the bonefixation element comprises a first snap interface and the first portioncomprises a second snap interface which is complementary to the firstsnap interface, wherein the first collet is secured within the firstpassageway by the complementary first and second snap interfaces.
 4. Thesystem of claim 3, wherein the bone fixation element comprises aplurality of successive snap interfaces, wherein the second snapinterface engages each successive snap interface of the bone fixationelement as the first collet slides farther within the first passageway.5. The system of claim 1, wherein the first portion comprises a firstcollet driver interface for attachment to a collet driver instrument. 6.The system of claim 1, wherein the first end comprises a first countertorque interface for complementary fit with a second counter torqueinterface of a counter torque instrument.
 7. The system of claim 1,wherein the second portion comprises a plurality of protrusions withinthe central bore.
 8. The system of claim 1, wherein the line passesthrough the first passageway, wherein the first working portion, thefirst collet, and the first passageway are coaxial.
 9. The system ofclaim 1, wherein, in the first engaged position, the first collet iscompletely within the bone fixation element.
 10. The system of claim 1,wherein, in the first engaged position, the first colletcircumferentially compresses around the first working portion withminimal deformation to the line, so as to hold the first working portionin a fixed position relative to the bone fixation element.
 11. Thesystem of claim 1, wherein the bone fixation element comprises a secondpassageway extending between the first and second ends, wherein thesecond working portion is secured to the bone fixation element withinthe second passageway.
 12. The system of claim 11, comprising: a secondcollet like the first collet, wherein the second collet is movable alongthe second passageway between a third engaged position and a fourthposition; wherein, in the third engaged position, the second workingportion of the line is held in a fixed position relative to the bonefixation element by the second collet, and the second collet is a thirddistance from the first end of the bone fixation element; wherein, inthe fourth position, the line slidably passes through the second collet,and the second collet is a fourth distance from the first end of thebone fixation element, wherein the fourth distance is greater than thethird distance.
 13. A system comprising: a bone fixation elementcomprising a first end, a second end opposite the first end, and firstand second passageways extending between the first and second ends; afirst collet comprising a first longitudinal central bore, wherein thefirst collet is movable along the first passageway between a firstengaged position and a second position; a second collet comprising asecond longitudinal central bore, wherein the second collet is movablealong the second passageway between a third engaged position and afourth position; and a line comprising a first working portion and asecond working portion connected to the first working portion, whereinthe first working portion passes through the first longitudinal centralbore, wherein the second working portion passes through the secondlongitudinal central bore; wherein, in the first engaged position, thefirst collet circumferentially engages the first working portion to fixthe first working portion to the bone fixation element; wherein, in thethird engaged position, the second collet circumferentially engages thesecond working portion to fix the second working portion to the bonefixation element.
 14. The system of claim 13, wherein the first colletis secured within the first passageway by threads.
 15. The system ofclaim 13, wherein the first collet is secured within the firstpassageway by snap interfaces.
 16. The system of claim 13, wherein thefirst collet comprises a protrusion in the first longitudinal centralbore.
 17. The system of claim 13, wherein the first and second colletseach comprise a first collet driver interface for attachment to a colletdriver instrument.
 18. The system of claim 13, wherein the bone fixationelement comprises a first counter torque interface around a firstopening for the first passageway, and a second counter torque interfacearound a second opening for the second passageway, wherein the first andsecond counter torque interfaces are for complementary fit with a thirdcounter torque interface of a counter torque instrument.
 19. The systemof claim 13, wherein, in the first engaged position, the first colletcircumferentially compresses around the first working portion withminimal deformation to the line.
 20. A system comprising: a bonefixation element assembly comprising: a bone fixation element comprisinga passageway, and a counter torque interface; and a collet comprising alongitudinal central bore, and a collet driver interface, wherein thecollet is movable along the passageway between a first engaged positionand a second position; and an instrument assembly comprising: a colletdriver comprising a collet driver handle, a collet engagement interfacein complementary engagement with the collet driver interface, and acollet driver shaft extending between the collet driver handle and thecollet engagement interface, wherein rotation of the collet driver movesthe collet along the passageway; and a counter torque instrumentcomprising a counter torque handle comprising a notch, a key incomplementary engagement with the counter torque interface, a countertorque shaft, and a counter torque bore extending longitudinally throughthe counter torque instrument, wherein the counter torque bore receivesthe collet driver shaft with clearance and the notch receives the colletdriver handle with clearance; wherein the counter torque instrumentprovides counter torque when the collet is moved along the passageway bythe collet driver tool.
 21. The system of claim 20, wherein the countertorque interface comprises a plurality of circular slots equally spacedaround an opening for the passageway.
 22. The system of claim 21,wherein the key comprises a plurality of prongs slidably engaged withthe plurality of circular slots.
 23. The system of claim 20, wherein thecollet driver interface comprises a shape selected from the groupconsisting of hexagon, square, and triangle.
 24. The system of claim 20,comprising: a line comprising a first working portion and a secondworking portion connected to the first working portion, wherein thefirst working portion passes through the longitudinal central bore,wherein the second working portion is secured to the bone fixationelement.
 25. The system of claim 24, wherein, in the first engagedposition, the first collet circumferentially compresses around the firstworking portion with minimal deformation to the line to fix the firstworking portion to the bone fixation element.
 26. The system of claim24, wherein the collet driver comprises a collet driver bore, whereinthe collet driver bore slidably receives the line.